A magnetic recording-reproducing system is popular in this field as a recording-reproducing system of information signals such as audio signals or video signals. However, the conventional magnetic recording-reproducing system is defective in that it is difficult to achieve a high recording density and a sufficiently high SN ratio.
A magnetic transcription-recording method is also known to the art as a method of rapidly reproducing from a single master recording medium the magnetic recording medium used in the magnetic recording-reproducing system. In the conventional magnetic transcription-recording method, the magnetic material layer of a magnetic recording medium is brought into contact with the magnetic material layer of a master recording medium having information signals recorded therein. Under this condition, a magnetic field is applied to these recording media so as to magnetically transcribe and record the information signals in the magnetic material layer of the magnetic recording medium. In the conventional method, however, the magnetic layer of the master recording medium has a smooth surface, with the result that slippage tends to occur during the transcription-recording operation between the two magnetic material layers. Naturally, the slippage deteriorates the information signals recorded in the recording medium, rendering it difficult achieve a satisfactory transcription-recording. For example, the SN ratio is lowered and cross-talk is generated between the recorded signals, particularly where the recording density is high.
Recently, a video disc has been developed, in which information signals are recorded by using laser beams or electron beams in a disc-shaped recording medium in a pattern of projections, hereinafter referred to as concave-convex pattern, and the recorded signals are reproduced mechanically electrostatically or optically. The video disc is approaching the stage of practical use. The recent machining technique using laser or electron beams permits forming a very fine concave-convex pattern of submicron order. Thus, the video disc permits achieving an extremely high recording density and also permits sufficiently increasing the SN ratio of the reproduced signals. In addition, the video disc can be readily reproduced from a single master disc by a pressing method.
However, a special apparatus is required for reproducing the information signals recorded in the video disc in a concave-convex pattern, whether the information signals are reproduced mechanically, electrostatically or optically. In addition, the reproducing apparatus is costly, compared with the magnetic reproducing apparatus popular in this field. What is more important is that some technical problems remain unsolved in the reproducing apparatus of a video disc, rendering it impossible to reproduce the recorded information signal stably and without fail.
To be brief, it is practically desirable to use a magnetic reproducing apparatus utilizing a simple magnetic head, which is widely employed nowadays and has already been technically accomplished. Thus, it is a matter of serious concern in this field to develop a magnetic recording medium capable of recording information signals at a high density and permitting the recorded information signal to be reproduced by a simple magnetic reproducing apparatus.
It should also be noted that the video disc described above is for reproduction alone. In contrast, the magnetic recording medium is capable of erasing the recorded information signal and recording again optional signals.
An object of this invention is to provide a magnetic transcription-recording method for reproducing from a single master recording magnetic recording media each capable of recording information signals at a high density, capable of permitting the recorded information signal to be reproduced by a magnetic reproducing apparatus, and capable of optically erasing the recorded information signal and recording again new information signals.